Hydraulic equipment for pushing and pulling rod or pipe is especially useful for installing underground conduit, such as wter and gas lines, with a minimum of excavation. When conduit must be placed under streets, lawns, or driveways, it may be highly impractical to excavate along the entire length of the conduit due to the destruction of property, rerouting of traffic, or great expense. Therefore, pipe pullers and pushers are well known in the art for driving pipe underground without the necessity of excavating more than a hole at each end of the pipe line.
The pipe pushers and pullers of the prior art have generally utilized a lever action for gripping the pipe. The gripping lever can be attached to a carriage that is mounted for reciprocating movement along rails of a frame. However, many of the gripping levers of presently available pipe pushers and pullers provide either insufficient gripping of the pipe or excessive shear force that can damage the outer surface of the pipe. This problem can be highly undesirable when the pipe or rod is intended for repeated use in tunneling underground conduit lines.
Therefore, a need has been identified for an hydraulic rod and pipe pusher-puller that grips the rod securely without damage during the power stroke, releases the rod completely during the reset stroke, and adjusts easily for providing pushing or pulling force on the rod.